模板与使用 模板就是使程序能够对不同类型的数据进行相同 方式的处理。C++中的模板分为类模板和函数模板 类模板 说明类模板的一般格式为:

§1.1 数据和信息 §1.2 土地信息 §1.3 信息系统和土地信息系统 §1.4 土地信息系统的发展与应用

assachusetts Institute of Technology Department of Electrical Engineering and Computer Science 6. 111-Introductory Digital Systems Laboratory Project resources Project resources are allocated on a per student basis. This means that a two-person

Massachusetts Institute of Technology Department of Electrical Engineering and Computer Science 6. 111-Introductory Digital Systems Laboratory Project Information Introduction The term project in 6 1 1 1 is your opportunity to specify a small digital system. You will

Data Link Layer (DLC) Responsible for reliable transmission of packets over a link Framing: Determine the start and end of packets(sec 2.5) Error Detection: Determine when a packet contains errors ( sec 2.3) Error recovery: Retransmission of packets containing errors(sec 2. 4) DLC layer recovery May be done at higher layer

Service times Poisson arrivals at rate n Service time has arbitrary distribution with given E[X] and E[X2I Service times are independent and identically distributed (ID) Independent of arrival times E[service time]=1/u Single Server queue

An interesting property of an M/M/ 1 queue, which greatly simplifies combining these queues into a network, is the surprising fact that the output of an M/M/ queue with arrival rate is a Poisson process of rate This is part of Burke's theorem, which follows from reversibility A Markov chain has the property that P[future present, past] P[future present] Conditional on the present state, future states and past states are independent

Multiple Access shared transmission medium a receiver can hear multiple transmitters a transmitter can be heard by multiple receivers the major problem with multi-access is allocating the channel between the users the nodes do not know when the other nodes have data to send Need to coordinate transmissions

Carrier Sense Multiple Access(CSMA) In certain situations nodes can hear each other by listening to the channel “Carrier Sensing CSMA: Polite version of Aloha Nodes listen to the channel before they start transmission Channel idle=> Transmit Channel busy = Wait (join backlog) When do backlogged nodes transmit? When channel becomes idle backlogged nodes attempt transmission with probability q=1 Persistent protocol, q=1 Non-persistent protocol,< 1

Optimal Routing View routing as\global\ optimization problem Assumptions: The cost of using a link is a function of the flow on that link The total network cost is the sum of the link costs The required traffic rate between each source-destination pair is known in advance Traffic between source-destination pair can be split along multiple paths with infinite precision